Posted
by
timothy
on Tuesday December 30, 2008 @06:59PM
from the sacred-cow dept.

Migraineman writes "NASA has released a 400-page Columbia Crew Survival Investigation Report [16MB PDF.] If you're interested in a detailed examination and timeline of the events leading to the destruction of Columbia, this is well worth the time. The report includes a number of recommendations to increase survivability of future missions." Reader bezking points out CNN's story on the report, which says that problems with the astronauts' restraint systems were the ultimate cause of death for the seven astronauts on board.

They knew all that mostly from a video of the re-entry taken seconds before the shuttle disintegrated. They didn't piece it together from the wreckage (apart from finding the video tape in the wreckage).

The report lists the immediate causes of death as depressurization, and then trauma (not properly restrained, or failure of restraint for upper body and head in sudden depressurization) for those who survived even that long.

Each event listed after is in of itself certain death, and the report makes sure to say that even if everyone were wearing their full equipment and had been properly restrained, there was no way to survive - there simply isn't a way for our current equipment to "eject" or have a "safety capsule."

The things we can take away are that all signs point to sudden, painless deaths well before breakup, and that the things learned in the investigation can be applied for greater safety in future missions.

But I will say one thing. I think the shuttles were an utter failure, a terrible engineering compromise between the original intention and what a combination of technological limits and Congressional pork barreling.

(boldface mine)

Lack of intelligent pork-barreling, more like it. If an important (read: expensive) part had been built in Wisconsin, Senator Wm. Proxmire wouldn't have, well, proxmired it down to the DC-1.5 level that it was. We might have had the original design with geosynchronus orbit capability.

We would have been much better off continuing from the Apollo programs, and putting off reusable vehicles until we were further down the road.

Continuing the Apollo program would have been a nice dream, but unfortunately, that is all that it could be. It was reduce the price to orbit or give up the program. As planned, the orbiter was expected to reduce the price per pound to LEO, even more than cheap expendables.

In April 2008 a Soyuz made an uncontrolled reentry due to failure of the service module to separate during the de-orbit sequence. The cosmonauts survived due to the inherent ballistic stability and fail-safety of the design:http://www.spectrum.ieee.org/may08/6229

NASA has finally conceded that the safest place for the astronauts is on top of the launch stack, with abort rockets to escape a failing lower stage, and with no exposure to damage from falling debris. These factors plus the increased safety of ballistic reentry explain the return to capsules with the Constellation system.

At 63,000 feet MSL, all the gases dissolved in your blood boils. You die in seconds if exposed to rapid decompression.

The Columbia began it's breakup around 200,000 feet MSL and most educated guestimates place the altitude where the pressurized crew compartment broke away from the rest of the craft at around 100,000 feet and that it held its pressure until about 60,000 feet until it broke open.

The ballistic trajectory of the big chunks of what was left of the ship took a sharp downward turn once it reached about 40,000 feet MSL due to all the pieces slowing down so rapidly and then fracturing into such small pieces as to next be more accurately called a debris cloud in the relatively thick atmosphere of 35,000 feet compared to where the breakup first began.... at least that's what the math models derived from the shape and size of the debris field on the ground seems to suggest.

One thing that always amazes me, and that most people don't even understand is that the actual atmospheric air pressure difference between here on the ground and being in the "vacuum" of space, is only 14.7 teeny-tiny pounds per square inch.That's right. Less than 15 measly PSI. Fifteen PSI ain't even enough air in your car tire to make it roll very well. And that's all the difference there is between ground and space. Space is not some huge gigantic super vacuum that'll crush a strong metal container as if it was a beer can. Space is actually a quite subtle difference in pressure from what we breath here on the surface, especially when you compare it the pressure difference to what you'd find a only a few thousand feet under the sea.

Capsules don't rely on tiles but instead use single-ablative shields that are protected during the entire flight until reentry.After each launch the shuttle has to be completely rebuilt so there weren't any cost savings.A little more about problems with the shuttle design by a Nobel-Prize winning physicist....

This report does absolutely nothing for the astronauts that tragically died. It attempts to extract valuable lessons for future endeavors.

The failure of the restraints under this circumstance is only significant in the context of future missions.

It means that future astronauts in a much less dire situation would be killed due to failure of their restraints even if no other mishaps beyond a temporary loss of control occurred. In this particular case, the TFA is pretty clear in pointing out that the crew was either dead or unconscious due to restraint failure which could have been prevented long before catastrophic breakup of the vehicle for which prevention is stated as the only remedy.

A loss of astronaut lives in an event that did not promulgate loss of the vehicle would be politically devastating and need not occur if more attention is paid to this system on future vehicles.

Terribly sorry to reply to my own post, but I located a Wikipedia article with useful information on this subject.
[wikipedia.org]
It would seem that in my previous post I was (at least partially) correct.

The claim that the initial "depressurization" would make the crew "incapacitated within seconds" relies on the common perception that exposure to the vacuum of space makes your face explode. That's not the case, as has been explained over and over -- you can't breathe (" respiration ceased after the depressurization" in the report), but not breathing hasn't been the criteria for "death" since the Middle Ages.

The concept there is Time of Useful Consciousness - which is how long a human can remain conscious when exposed to high altitudes. For someone taken from essentially sea level (whatever the shuttle normally is) to 200,000 feet that time is going to be very, very short - probably on the order of seconds. Even at normal fighter altitudes of 40-50,000 feet the TUC is 9-12 seconds, and it is even lower (up to 50% lower) in the case of a rapid decompression, which this almost certainly was.

Spaceplanes don't have to use a ceramic tile, just the space shuttle, the way they designed it required either ceramic tiles or reusable ablative coverings (which was optional in the design for a while in case the ceramic tiles turned out to be impossible, but hasn't been mentioned since)

One aspect of the X-33 that never got tested (which bugs me) is the reusable refractory metallic heat shield. See, the denser the craft, the gentler the reentry. If the shuttle was less dense, perhaps by having the orbiter integrate at least some of the external tank's capacity, it might have been possible to make one with a less delicate shield.

The main reason why the ablative non-metallic heat shields on capsules are essentially foolproof is that you re-enter on a piece of shielding that's been kept covered the whole flight. You could likely make a capsule with a reinforced-carbon-carbon reusable shield if it weren't likely to shatter when it hits the ground.

I'd also like to point out that, on average, the skin has a surface area of 16.1 to 21.5 sq ft. At 14.5 psi (pounds per square inch, average atmospheric pressure) that's 233 to 312 pounds of force keeping you from exploding.

The numbers are basically correct (the "your blood boils and you die within seconds" stuff is not). Pilots use the term "useful consciousness" [wikipedia.org] to describe the timespan between rapid decompression of the plane and the time at which you can no longer perform basic tasks (like putting on your oxygen mask). At 11,000 meters, this time is down to something like 20 seconds. Which is the reason why oxygen masks are automatically deployed in such a case -- there just wouldn't be enough time to manually obtain them from a storage tank or something like that.

at 63,000 is the Armstrong Line or Armstrong Limit. The oxygen in your blood "boils" out, in that it turns into vapor. Now, let's see, air we breathe passes in and out of our lungs...see a problem here? What a rapid decompression results in is damage to the lungs (and heart and CNS). No delicate way to put it. The lungs "explode". Now, let's not think Hollywood special effects. Each little--okay, many--little airsacs in the lungs rupture from differential pressure. This is called ebullism. For you reference folk, check out Wikipedia Armstrong Limit, although the entry there isn't entirely correct, or more accurately, complete. More importantly check out its 2nd reference. Here is the reference for simplicity: http://www.geoffreylandis.com/ebullism.html [geoffreylandis.com]
It's not crap, folk. It's physics.

I mean this thing exploded, or better yet disintegrated how many hundreds (thousands) of meters in the sky, scattered its debris all over BFE, and yet they can still piece together enough information to deduce who was unbuckled, who wasn't wearing gloves, and who didn't have their visors down.

They knew all that mostly from a video of the re-entry taken seconds before the shuttle disintegrated. They didn't piece it together from the wreckage (apart from finding the video tape in the wreckage).

Actually, if you read the report (as I just spent the entire afternoon reading), you'll find that they *did* piece it together from the wreckage, because they *had* to. The [onboard] video ends just after Entry Interface - 15 minutes *before* Loss Of Signal, which was in turn 46 seconds before the Columbia broke up. (And it would be another 35 seconds before the crew compartment broke up.) Lots of time for gloves to be locked in place, buckles to be tightened down, visors to be closed and locked...

You know, for an 'inherently flawed and unsafe design' it did pretty well for almost 30 years, outliving it's expected life by, what, 15?

The Shuttles lifetime was based on number of flights, not number of years of service. In that light, the Shuttle fleet has flown less than half of its design lifetime.

Regarding capsules, you're not exactly going to survive uncontrolled re-entry if, say, a tile breaks off or the parachutes fail to deploy.

Capsules didn't have tiles, they had one-piece, single-use ablative shields. Given their single-use nature, they could be engineered robustly. Contrast that with Shuttle TPS tiles, which are so fragile you can damage one by pressing on it too hard with a finger. But they had to be fragile in order to be light enough to be reusable.

Regarding parachute failure, every capsule has multiple redundant parachute systems. Sure, all of them could have simultaneously failed, but that would be extremely unlikely. Contrast that with the Shuttle TPS, where a critical tile failure would invariably cause total loss of vehicle, mission, and crew. The difference here is not in the overall danger, it's in the safety margin. Capsules had more redundancies, simpler designs, and fewer compromises placed upon them. The Shuttle tried to be all things to all people and ended up being a compromise at everything it tried to do.

We've just had less capsule launches than shuttle launches.

And you could play Russian Roulette once an hour, every hour, for thirty years and not blow your head off. Statistically it's unlikely, but it's entirely possible.

NASA rolled the dice every time a Shuttle launched, and NASA did it knowing that the Shuttle's design required it to violate the engineering assumptions in order to operate. Specifically, the Shuttle design requirements stated categorically that "no debris" could impact the TPS during launch. This flew in the face of simple physics: the TPS is only a few feet away from a tank full of supercold liquid hydrogen and oxygen, and Florida's humid climate virtually guarantees ice accumulation on the tank...ice which will flake off during launch and likely impact the TPS, the boosters, the tank, or all three. Historical tile damage reports indicate this happened from the very first Shuttle launch onwards, but NASA just accepted it and kept on launching.

Tile design guidelines specifically stated they were not designed to withstand any significant impact. Yet NASA continued to operate the Shuttle outside its design criteria for years. They did the same thing with O-ring burn throughs until Challenger caught up with them. Columbia's disaster was rooted in a similar history, where many other flights were near disasters had debris impacted an inch to the left here or an inch to the right there.

The Shuttle's "fantastic" safety record is much more attributable to luck than anything remotely resembling a good design.